1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to elevator systems which include an access control system or security terminal.
2. Description of the Prior Art
It is common in elevator systems to select at least one elevator car from a bank of cars to operate in a night-time security mode. Still other elevator systems may operate in a security mode at all times, for all floors, or for certain specified floors, depending upon the building and its usage. In such systems, a suitable access control system or security terminal is usually located at the main floor or lobby of the associated building, which operates in conjunction with the supervisory control or system processor of the elevator system. When the elevator system is placed on security mode, a prospective passenger must provide a predetermined security input to this access control system in order to gain access to at least certain of the floors displaced from the main or lobby floor. Upon recognizing a proper security input, the security terminal causes the supervisory control or system processor for the elevator system to enable a certain floor, or floors, that the individual is authorized to gain access to. In order to provide prompt service to the next prospective passenger, the supervisory control system must then monitor the call serving process, starting with the placement of the car call by the individual for an enabled floor, and ending with the completion of service to the enabled floor. If the building has certain floors which operate continuously in security mode, and others which do not, continuous monitoring of the security calls adds substantially to the complexity and cost of the elevator system, and it increases the running time of the group supervisory program for an elevator system processor which is computer controlled. Merely enabling the selected floor for a predetermined period of time is inefficient, as the time must be selected for the maximum run. On shorter runs, the security car will sit idle until its time expires, delaying service to the next passenger. If the car is delayed by the passenger holding the doors, etc., the floor enable time may expire before the car even reaches the destination floor.
Thus, it would be desirable to provide a new and improved access control system for elevators which may be quickly and easily applied to new, or existing elevator systems. The system should have a low initial cost, and it should place little additional burden on the group supervisory control or system processor of the elevator system, facilitating use of the system in buildings which have security controlled floors during the normal working day, as well as in buildings which use the security mode only after normal hours, and on weekends.